This chapter is from the book

This chapter is from the book

Over the next five chapters, you are going to build an application named WorldTrotter. When it is complete, this app will convert values between degrees Fahrenheit and degrees Celsius. In this chapter, you will learn about views and the view hierarchy through creating WorldTrotter’s user interface. At the end of this chapter, your app will look like Figure 3.1.

Figure 3.1 WorldTrotter

Let’s start with a little bit of the theory behind views and the view hierarchy.

View Basics

Recall from Chapter 1 that views are objects that are visible to the user, like buttons, text fields, and sliders. View objects make up an application’s user interface. A view

is an instance of UIView or one of its subclasses

knows how to draw itself

can handle events, like touches

exists within a hierarchy of views whose root is the application’s window